Changing travis file to avoid infinite loop of npm install

Author: lmammino

.travis.yml

@@ -4,7 +4,17 @@ node_js:
   - "6"
   - "5"
   - "4"
+env:
+  - CXX=g++-4.8
+addons:
+  apt:
+    sources:
+      - ubuntu-toolchain-r-test
+    packages:
+      - g++-4.8
 script:
   - npm test
 install:
   - npm install --dev
+before_install:
+  - "npm update -g npm"